1. Field of the Invention
The present invention relates to a method for manufacturing a liquid jet recording head for generating the recording droplets used for an ink jet recording method.
2. Related Background Art
A liquid jet recording head applicable to an ink jet recording method (liquid jet recording method) is generally provided with fine recording liquid discharging ports (synonymous with "orifices"), liquid flow passages, and the liquid discharging energy generating portions which are arranged on a part of each of the foregoing liquid flow passages. As the method for manufacturing a liquid jet recording head such as this, there has hitherto been known a method wherein a glass or metallic plate is used, for example, and subsequent to the formation of fine grooves on such plate by means of cutting, etching, or other machining, the plate on which the grooves are formed is joined to the other appropriate plate for the formation of the liquid flow passages.
However, the liquid jet recording head manufactured by a conventional method of the kind tends to result in the inner wall surfaces of the liquid flow passages having an undesirable roughness, or in the deformation of the liquid flow passages due to the difference in the etching ratio. Thus, it is difficult to obtain the liquid flow passages having a constant resistance in them, leading to a problem that the recording characteristics of the liquid jet recording heads tend to vary after the manufacture. Also, in cutting, the plate is easily broken or is apt to crack; thus resulting in an undesirable manufacturing yield. Also, in etching, the number of processes is many so that there is a disadvantage that the cost of manufacturer is increased. Furthermore, in the conventional method as described above, when it is needed to precisely bond the grooved plate for the formation of the liquid flow passages and the covering plate for the provision of the driving elements such as piezoelectric elements or electrothermal transducers to generate the energy for discharging the recording droplets, there is a difficulty in positioning them as a common drawback. Hence, a problem is inevitably encountered that the conventional method lacks in the mass productivity.
Also, the liquid jet recording head is always in contact with a recording solution (usually, an ink liquid which is mainly composed of water and is not neutral in most cases, an ink liquid which is mainly composed of an organic solvent, or the like) when the head is in use. As a result, the material to construct a head for the liquid jet recording should desirably be the one which is not easily affected by the recording solution in keeping its strength. Also, on the contrary, the material should not create any harmful component which may be mixed in the recording solution to reduce its capability as a recording liquid. In the above-mentioned conventional method, there is a limit due to the method of machining, and it is difficult to select a material which meets these requirements perfectly after all.
In order to solve the problems, there has been designed a method as disclosed in Japanese Laid-Open Patent Application Nos. 57-208255 and 57-208256 wherein the nozzles comprising ink flow passages and orifice portions are patterned on the photosensitive resin substrate on which the ink discharging pressure generating elements are formed, and then, a glass plate ceiling or the like is joined onto this substrate.
Nevertheless, this method has the problems given below.
(1) A bonding material for the adhesive bonding of the ceiling plate drops and flows into the ink flow passages to deform shapes of the flow passages.
(2) In cutting the foregoing substrate to form the ink discharging ports, the cut particles enter the ink flow passages, resulting in the unstable ink discharge.
(3) Since the substrate having the hollow portion where the ink flow passages are formed is cut, the ink discharging ports are partially cut off when formed by cutting.
Because of these problems, the manufacturing throughput of the liquid jet recording head is not only reduced, but also it is difficult to manufacture a liquid jet recording head having a finer structure of the ink flow passages or a more number of ink discharging ports for an elongated head.
As a method to avoid these problems, it is possible to cite an invention disclosed in Japanese Laid-Open Patent Application No. 61-154947. This invention is such that the ink flow passages are formed by a soluble resin, and the pattern thus formed is covered with an epoxy resin and hardened, and then, after the substrate is cut, the soluble resin pattern is removed by elution.
On the other hand, with the progress in the recording technology in recent years, a higher precision is increasingly demanded, and in the industrial field of the liquid jet recording, the reduction of the orifice area is being attempted as a method to meet such a demand. In other words, there is a need for a machining technique to produce finer orifices.
Here, according to the methods disclosed in the foregoing Japanese Laid-Open Patent Application No. 57-208255, Japanese Laid-Open Patent Application No. 57-208256, and Japanese Laid-Open Patent Application No. 61-154947, respectively, it is equally required to cut the ink flow passages to form the ink discharging ports. Thus, the distance between the ink discharging pressure generating elements and the discharging ports depends on the precision with which to cut the ink flow passages. In the meantime, it is generally practiced that the cutting is performed by a dicing saw or the like mechanical means. It is difficult to implement a high precision cutting. Also, in cutting, a cut off may occur for the substrate, and there are some cases where a curved ink discharging results, making it difficult to implement a desirable printing.
On the other hand, the irradiation of a laser light is used for machining in the method wherein the ink discharging ports are opened on a plate or the like, and then, such plate is joined to the end of the ink flow passages to form a recording head. However, in the laser machining, the opening is formed with a taper. As a result, depending on the direction of the taper (wider or narrower toward the outside when observed from the ink flow passage side), there may occur an unstable state of the ink discharge.